Growing emphasis on increasing the reservoir recovery factor for subsea well operations provides a stimulus for separation of water from produced hydrocarbons. Additionally, onshore wells very often have to cope with significant water breakthrough (70-80%+ of water in oil (WiO)). Fundamentally, water separation provides significant operational efficiency gains.
Water separation provides for reduction of back pressure on the reservoir by reduction of static hydraulic head (i.e., lower specific gravity of produced fluid in the pipeline, which can be significant in deeper waters and deeper reservoirs) and reduced frictional effects in the subsea pipeline. It may operate at a lower relative flowrate than for the combined oil+effluent volume. The reduction of back pressure on the reservoir and the reduced frictional effects in the subsea pipeline provide an opportunity for increasing total reservoir recovery over field life, by reducing field abandonment pressure, and/or deferring the time at which pressure boosting might be considered necessary, where feasible.
Water separation allows for the reduction in size of export flowline(s) for a given scenario. Reduction in size of export flowline(s) can significantly reduce the total installed cost of the pipeline, particularly on subsea developments where pipeline costs are always a predominant cost factor. Water separation also reduces dependence on chemical injection, which is otherwise required for hydrate mitigation. By eliminating dependence on chemical injection, consumables cost over field life may be reduced.
A need exists for a technique that addresses the emphasis on increasing the reservoir recovery factor for subsea well operations by separation of water from produced hydrocarbons. A new technique in necessary to simplify total system installation and to provide available separation capacity at the earliest point in field life without disruption to production. The following technique may solve one or more of these problems.